i added some custom sorting filters to woocommerce to sort my own product group. the filter is shown in woo-backend, but does not show in the product grid frontend as an option. may you have an idea? here is the code i use to add the filter:

You just need to copy the entire avia_woocommerce_frontend_search_params function (located in /config-woocommerce/config.php) into your child theme functions.php file. Then modify the function code there. The child theme file will be loaded first and your custom sort function will overwrite the code in the parent theme files because we wrapped all functions into a function_exists() if statement. If you need help with the code implementation please hire a freelancer. I recommend a platform like: http://studio.envato.com/